Field of the Invention
The present invention relates to a radio-controlled timepiece.
Description of the Related Art
Conventionally, there has been an electronic timepiece (radio-controlled timepiece) which is able to obtain date/time data from an external date/time information source to correct date and time kept by a timekeeping circuit. Examples of such external date/time information source include, a transmitting radio wave from a navigation satellite (positioning satellite) used in a Global Navigation Satellite System (GNSS, positioning system), a transmitting radio wave of a standard radio wave transmitting station which transmits time information with a radio wave having a long waveband, date/time information output from a wired or wireless server (NTP server) on the Internet, date/time information obtained by a cellular phone from a base station of the cellular phone and received from the cellular phone by short distance wireless communication, and the like. Such external date/time information source each have their advantages and disadvantages regarding accuracy, easiness of reception, time necessary for reception, electric power consumed in reception, and the like. Therefore, conventionally, there is an electronic timepiece which uses a plurality of methods to obtain date/time information in order to support the disadvantages (for example, Japanese Patent No. 3796380, Japanese Patent Application Laid-Open Publication No. 2002-71854).
Such radio-controlled timepiece obtains the date/time information from outside at a suitable recurrence so that normally, the error can be maintained at a very small degree. However, a leap second may be inserted or deleted from the date and time employed worldwide at present. The timing that insert or delete of the leap second can be executed is set at directly before 00:00:00 on January 1st or July 1st in Coordinated Universal Time (UTC). The insert or delete of the leap second is executed as necessary based on the time of the UTC and difference in culmination time due to rotation of the Earth, and the time is shortened or lengthened for 1 second.
Such delete or insert of the leap second is performed irregularly, and is not always executed each time. Therefore, timepieces which do not obtain information regarding the insert or delete of the leap second in advance cannot judge whether there is a delete or insert of the leap second. Therefore, after the insert or delete is executed, the time is counted and displayed with a difference in the amount of 1 second.
The date and time (GPS timepiece) counted in each GPS satellite and transmitted in the radio wave transmitted from the positioning satellite (GPS satellite) of the Global Positioning System (GPS) does not consider the above described insert and delete of the leap second. Various correction parameters for the date/time data are transmitted from the GPS satellite. Information regarding the added value of the leap second executed from a predetermined timing (Jan. 6, 1980) is included in the correction parameters. Therefore, the new added value needs to be obtained after the insert or delete of the leap second is executed, otherwise the correct present date and time cannot be calculated from the date/time data of the GPS timepiece.
However, the data of the UTC correction parameter including the correction parameter regarding the leap second is transmitted only once every 12.5 minutes in the transmitting radio wave from the GPS satellite. When a portable radio-controlled timepiece, specifically, a timepiece which uses a small battery such as a watch is used, it is difficult to receive satellite radio waves for a long period of time because a large amount of electric power needs to be consumed compared to the electric power consumed for other various operation in the timepiece. In view of the above, according to the technique disclosed in Japanese Patent No. 5114936 and Japanese Patent No. 5200636, after the information regarding the date and time is obtained, the interval of time until the transmitting timing of the UTC correction parameter is calculated, and after the reception is paused, the reception is performed again at the transmitting timing of the UTC correction parameter to suppress the electric power consumption.
According to the technique disclosed in Japanese Patent Application Laid-Open Publication No. 2011-208946, after the timing that the leap second can be executed, a notification that the displayed date and time may not be accurate is displayed until an accurate date and time is obtained from outside.
However, since the insert or delete of the leap second is not always executed, receiving the date/time data each time after the above timing regardless of whether the insert or delete of the leap second is executed and confirming the leap second results in increase of electric power consumption.